For these plastic canisters, closures have been developed which are described, for example, in U.S. Pat. No. 3,844,456. Such closures can be opened and closed very rapidly with a single motion of the hand. This is very important in emergency situations. The lid of the closure does not interfere with the pouring and it does not get lost. Such closures withstand drops without losing their tightness. The construction of these closures also makes it possible to arrange the air tubes advantageously so that the liquids run out with a minimum of gurgling. Moreover, they also run out quickly with such an arrangement because no air has to be drawn in through the actual discharge opening.
Furthermore, sheetmetal canisters have become known in which from the upper portion of the canister an annular hole is cut out near the handles. Sheetmetal canisters must always be welded together from at least two parts in order to form a hollow body. Since the circular cutout is located symmetrically in the center and is, moreover, relatively large, it is in no case possible at that point to tolerate a sheetmetal fold which after all would have to be welded. Into the circular cutout, an annular flange with an internal thread is welded liquid-tight. The internal thread serves to receive the external thread of a screw-cap with which the canister is closed. However, the main purpose of the thread is to make it possible to screw in place a coupling piece so that the canister can be connected to a motor fuel supply system which pumps the required fuel out of the canister. In this manner, there is no need to pour the canister content into a tank. The annular flange has a perforation in the region close to the handles. This perforation is butted on the inside by a vent tube. To attach this tube, in addition, by welding would mean an excessive crowding together of welded joints so that there exists the danger that the directly adjacent internal thread is warped out of shape. Closing the container with the screw cap requires three and a half turns and thus takes a relatively long time. The screw cap may be seated very firmly. In order to make it possible to move it a few degrees of angle even with a hitting tool, four flaps have been rolled up along the outer circumference of the screw cap. The screwing on is impeded by the fact that a wire rod is provided which originates from the center of the screw cap, extends far beyond the screw cap and is fastened to the handles by a small chain or the like. The screw cap can, therefore, not be turned freely.
The screw cap has a rubber ring which has almost an I-cross section and sits with its internal circumference on the external thread provided at the external circumference of a cup which is sunk into the screw cap. This gasket ring also has the function of sealing the vent hole. The gasket ring is acted upon by very large pulling forces when the screw cap is tightened firmly or loosened. As a result, the gasket ring ages rapidly.